Conformal deposition of silicon carbide films using heterogeneous precursor interaction

ABSTRACT

A doped or undoped silicon carbide film can be deposited using a remote plasma chemical vapor deposition (CVD) technique. One or more silicon-containing precursors are provided to a reaction chamber. Radical species, such as hydrogen radical species, are provided in a substantially low energy state or ground state and interact with the one or more silicon-containing precursors to deposit the silicon carbide film. A co-reactant may be flowed with the one or more silicon-containing precursors, where the co-reactant can be a depositing additive or a non-depositing additive to increase step coverage of the silicon carbide film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 14/616,435, filed Feb. 6, 2015, titled “CONFORMAL DEPOSITION OFSILICON CARBIDE FILMS,” (Attorney Docket No. LAMRP175/3576-1US), whichis a continuation-in-part of both U.S. patent application Ser. No.13/494,836, filed Jun. 12, 2012, titled “REMOTE PLASMA BASED DEPOSITIONOF SiOC CLASS OF FILMS,” (Attorney Docket No. NOVLP466/NVLS003722) andU.S. patent application Ser. No. 13/907,699, filed May 31, 2013, titled“METHOD TO OBTAIN SiC CLASS OF FILMS OF DESIRED COMPOSITION AND FILMPROPERTIES,” (Attorney Docket No. LAMRP046/3149), each of which isincorporated herein by reference in its entirety and for all purposes.

BACKGROUND

The silicon carbide (SiC) class of thin films has unique physical,chemical, and mechanical properties and is used in a variety ofapplications, particularly integrated circuit applications. Classes ofSiC thin films include oxygen doped silicon carbide, also known assilicon oxycarbide, nitrogen doped silicon carbide, also known assilicon nitricarbide, and oxygen and nitrogen doped silicon carbide,also known as silicon oxynitricarbide, and undoped silicon carbide.

The background provided herein is for the purposes of generallypresenting the context of the disclosure. Work of the presently namedinventors, to the extent that it is described in this background, aswell as aspects of the description that may not otherwise qualify asprior art at the time of filing, are neither expressly nor impliedlyadmitted as prior art against the present disclosure.

SUMMARY

Provided herein is a method of depositing a silicon carbide film on asubstrate. The method includes providing a substrate in a reactionchamber, flowing a silicon-containing precursor into the reactionchamber towards the substrate, and flowing a co-reactant into thereaction chamber along with the silicon-containing precursor. Thesilicon-containing precursor has (i) one or more Si—H bonds and/or Si—Sibonds, (ii) one or more Si—C bonds, Si—N, and/or Si—O bonds, (iii) noC—O bonds, and (iv) no C—N bonds. The co-reactant is a hydrocarbonmolecule. The method further includes generating, from a hydrogen sourcegas, radicals of hydrogen in a remote plasma source that are generatedupstream of the silicon-containing precursor and the co-reactant, andintroducing the radicals of hydrogen into the reaction chamber andtowards the substrate, where the radicals of hydrogen are in a groundstate to react with the silicon-containing precursor and the co-reactantto form a doped or undoped silicon carbide film on the substrate, wherethe doped or undoped silicon carbide film has a conformality of at least90%.

In some implementations, all or substantially all of the radicals ofhydrogen in an environment adjacent to the substrate are radicals ofhydrogen in the ground state. In some implementations, the doped orundoped silicon carbide film is a doped silicon carbide film of siliconoxycarbide (SiCO), silicon carbonitride (SiCN), or siliconoxycarbonitride (SiOCN). In some implementations, the hydrocarbonmolecule has one or more carbon-to-carbon double bonds or triple bonds.The hydrocarbon molecule can include propylene, ethylene, butene,pentene, butadiene, pentadiene, hexadiene, heptadiene, toluene, benzene,acetylene, propyne, butyne, pentyne, or hexyne. In some implementations,the silicon-containing precursor and the co-reactant are simultaneouslyflowed along the same flow path into the reaction chamber. In someimplementations, the silicon-containing precursor includes analkylcarbosilane, a siloxane, or a silazane.

Another aspect involves a method of depositing a silicon carbide film ona substrate. The method includes providing a substrate in a reactionchamber, flowing a first organosilicon precursor into the reactionchamber, and flowing a second organosilicon precursor into the reactionchamber. The first organosilicon precursor has (i) one or more Si—Hbonds and/or Si—Si bonds, and (ii) one or more Si—C bonds, Si—N bonds,and/or Si—O bonds, and the second organosilicon precursor includes (i)no Si—H bonds and (ii) no Si—Si bonds. The method further includesgenerating, from a hydrogen source gas, radicals of hydrogen in a remoteplasma source that are generated upstream of the first organosiliconprecursor and the second organosilicon precursor, and introducing theradicals of hydrogen into the reaction chamber and towards thesubstrate, where the radicals of hydrogen are in a ground state to reactwith the first organosilicon precursor and the second organosiliconprecursor to form a doped or undoped silicon carbide film on thesubstrate.

In some implementations, all or substantially all of the radicals ofhydrogen are radicals of hydrogen in the ground state. In someimplementations, the doped or undoped silicon carbide film is a dopedsilicon carbide film of silicon oxycarbide (SiCO), silicon carbonitride(SiCN), or silicon oxycarbonitride (SiOCN). In some implementations, aflow rate of the second organosilicon precursor is at least two timesgreater than a flow rate of the first organosilicon precursor. In someimplementations, the doped or undoped silicon carbide film has aconformality of at least 95%. In some implementations, the secondorganosilicon precursor includes tetramethylsilane (4MS). In someimplementations, the first organosilicon precursor and the secondorganosilicon precursor are simultaneously flowed along the same flowpath into the reaction chamber.

These and other aspects are described further below with reference tothe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional schematic of an example doped orundoped silicon carbide film deposited over a substrate.

FIG. 1B illustrates a cross-sectional schematic of an example doped orundoped silicon carbide film conformally deposited on features of asubstrate.

FIG. 1C illustrates a cross-sectional schematic of example doped orundoped silicon carbide vertical structures on sidewalls of a gateelectrode of a transistor.

FIG. 1D illustrates a cross-sectional schematic of example doped orundoped silicon carbide vertical structures on exposed sidewalls ofcopper lines in an air gap type metallization layer.

FIG. 1E illustrates a cross-sectional schematic of example doped orundoped silicon carbide pore sealants for porous dielectric materials.

FIG. 2 illustrates chemical structures of examples of representativecaged siloxane precursors.

FIG. 3 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some implementations.

FIG. 4 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some otherimplementations.

FIG. 5A shows a TEM image of a silicon carbide thin film deposited onsubstrate features without using a carbon-containing non-depositingadditive.

FIG. 5B shows a TEM image of a silicon carbide thin film deposited onsubstrate features using a carbon-containing non-depositing additive.

FIG. 6A shows a TEM image a silicon carbide thin film deposited onsubstrate features without using a silicon-containing depositingadditive.

FIG. 6B shows a TEM image of a silicon carbide thin film deposited onsubstrate features using a silicon-containing depositing additive.

DETAILED DESCRIPTION

In the present disclosure, the terms “semiconductor wafer,” “wafer,”“substrate,” “wafer substrate,” and “partially fabricated integratedcircuit” are used interchangeably. One of ordinary skill in the artwould understand that the term “partially fabricated integrated circuit”can refer to a silicon wafer during any of many stages of integratedcircuit fabrication. A wafer or substrate used in the semiconductordevice industry typically has a diameter of 200 mm, or 300 mm, or 450mm. The following detailed description assumes the present disclosure isimplemented on a wafer. However, the present disclosure is not solimited. The work piece may be of various shapes, sizes, and materials.In addition to semiconductor wafers, other work pieces that may takeadvantage of the present disclosure include various articles such asprinted circuit boards and the like.

Introduction

Manufacture of semiconductor devices typically involves depositing oneor more thin films on a substrate in an integrated fabrication process.In some aspects of the fabrication process, classes of thin films suchas silicon carbide, silicon oxycarbide, silicon nitricarbide, andsilicon oxynitricarbide are deposited using atomic layer deposition(ALD), chemical vapor deposition (CVD), plasma-enhanced chemical vapordeposition (PECVD), or any other suitable deposition method. As usedherein, the term silicon carbide includes undoped or doped siliconcarbides, such oxygen doped silicon carbide (SiCO), nitrogen dopedsilicon carbide (SiCN), and nitrogen and oxygen doped silicon carbide(SiOCN). For many, doped silicon carbides have at most about 50% atomicof dopant atoms, whether those atoms are oxygen, nitrogen, or atoms ofanother element. The doping level provides desired film properties.

Precursor molecules for depositing silicon carbides can includesilicon-containing molecules having silicon-hydrogen (Si—H) and/orsilicon-silicon (Si—Si) bonds, and silicon-carbon (Si—C) bonds.Precursor molecules for depositing silicon oxycarbides includesilicon-containing molecules having silicon-hydrogen (Si—H) bonds and/orsilicon-silicon (Si—Si) bonds, and silicon-oxygen (Si—O) bonds and/orsilicon-carbon (Si—C) bonds. Precursor molecules for depositing siliconnitricarbides include silicon-containing molecules havingsilicon-hydrogen (Si—H) bonds and/or silicon-silicon (Si—Si) bonds, andsilicon-nitrogen (Si—N) bonds and/or silicon-carbon (Si—C) bonds.Precursor molecules for depositing silicon oxynitricarbides includesilicon-containing molecules having silicon-hydrogen (Si—H) bonds and/orsilicon-silicon (Si—Si) bonds, and silicon-nitrogen (Si—N) bonds,silicon-oxygen (Si—O) bonds, and/or silicon-carbon (Si—C) bonds. CurrentPECVD processes may use in situ plasma processing in which a plasma isprovided directly adjacent to a substrate.

It has been found that depositing high-quality silicon carbide thinfilms can have certain challenges, such as providing films withexcellent step coverage, low dielectric constants, high breakdownvoltages, low leakage currents, high porosity, and/or coverage overexposed metal surfaces without oxidizing the metal surfaces.

While this disclosure is not limited by any particular theory, it isbelieved that the plasma conditions in typical PECVD processes fragmentthe silicon-containing precursor molecules in a manner that producesundesirable effects. For example, PECVD may break Si—O and/or Si—C bondsin the precursor molecules to produce highly reactive radicals or otherfragment types having high sticking coefficients. The fragments of theresulting doped silicon carbide film can include silicon, carbon, and/oroxygen atoms with bonds that are “dangling,” meaning that silicon,carbon, and/or oxygen atoms have reactive unpaired valence electrons.High sticking coefficients of the precursor molecules and theirfragments can deposit silicon carbide films with poor step coverage, asreactive precursor fragments may disproportionately stick to the upperregions of sidewalls and other structures in recessed features.

The dangling bonds can produce silanol groups (Si—OH) in a depositedsilicon oxycarbide or silicon oxynitricarbide film. As a result, thefilm may have detrimentally high dielectric constants. Film quality mayalso suffer because the direct plasma conditions tend to extract carbonout of the deposited film.

Furthermore, the dangling bonds can produce increased silicon-hydrogenbonding (Si—H) in deposited silicon carbide films. Broken bonds of Si—Ccan be replaced with Si—H in direct plasma deposition conditions. Thepresence of Si—H bonds in silicon carbide films can produce films withpoor electrical properties. For example, the presence of Si—H bonds canreduce breakdown voltages and can increase leakage currents because theSi—H bonds provide a leakage path for electrons.

Further, the dangling bonds can lead to uncontrolled chemical ormorphological structures in the silicon carbide films. In some cases,such structures are dense filaments having low or no porosity, such thatthe film has an unacceptably high dielectric constant. The lack ofporosity can be the result of the direct plasma conditions breaking Si—Cand/or Si—O bonds in cyclic siloxanes that would otherwise provideporosity in an ultralow-k dielectric material.

Direct plasma conditions sometimes employed in PECVD can lead todirectionality in the deposition because the energy to break up theprecursor molecules can be a low frequency which creates a lot of ionbombardment at the surface. The directional deposition can also lead todeposition of silicon carbide films with poor step coverage. A directplasma is a plasma in which the plasma (electrons and positive ions atan appropriate concentration) reside in close proximity to the substratesurface during deposition, sometimes separated from the substratesurface by only a plasma sheath.

Typical PECVD processes are sometimes inappropriate for depositingsilicon carbide films over exposed copper or other metal surfacesbecause such processes can oxidize metal. The PECVD process may useoxidants such as oxygen (O₂), ozone (O₃), carbon dioxide (CO₂), or otheroxidizing species to form a silicon oxycarbide film.

Environment at the Substrate Surface During Deposition

FIG. 1A illustrates a cross-section of an example silicon carbide filmdeposited over a substrate. The silicon carbide film 101 can be formedunder process conditions producing a relatively mild environmentadjacent to the substrate 100. The substrate 100 can be any wafer,semiconductor wafer, partially fabricated integrated circuit, printedcircuit board, display screen, or other appropriate work piece. Theprocess for depositing the silicon carbide film 101 can involve one ormore silicon-containing precursors having one or more Si—H bonds and/orone or more Si—Si bonds, along with other bonds such as Si—C bonds, Si—Obonds, and/or Si—N bonds, depending on the type of doped structure to beproduced.

Certain applications employing silicon carbide films are depicted inFIGS. 1B-1E. In some embodiments, the silicon-containing precursors caninclude silicon-oxygen containing precursors, silicon-nitrogencontaining precursors, and/or silicon-carbon containing precursors. Thesilicon-oxygen containing precursors can include one or more Si—O bonds,the silicon-nitrogen containing precursors can include one or more Si—Nbonds, and the silicon-carbon containing precursors can include one ormore Si—C bonds. In some embodiments, for example, thesilicon-containing precursors can include a single reactant A with Si—Oand Si—C bonds, or Si—N and Si—C bonds. In some embodiments, thesilicon-containing precursors can include a reactant B with Si—O bondsor Si—N bonds, and a reactant C with Si—C bonds. It will be understoodthat any number of suitable reactants may be employed in the scope ofthis present disclosure. The chemical structures of examplesilicon-containing precursors are discussed in further detail below.

The silicon-containing precursor includes one or more Si—H bonds and/orone or more Si—Si bonds. However, it will be understood that additionalsilicon-containing precursors may not necessarily include Si—H or Si—Sibonds. These additional silicon-containing precursors may be providedconcurrently with the silicon-containing precursor having one or moreSi—H and/or Si—Si bonds. During the deposition process, the Si—H bondsand/or Si—Si bonds are broken and serve as reactive sites for formingbonds between the silicon-containing precursors in the deposited siliconcarbide film 101. The broken bonds can also serve as sites forcross-linking during thermal processing conducted during or afterdeposition. Bonding at the reactive sites and cross-linking can form aprimary backbone or matrix collectively in the resulting silicon carbidefilm 101.

In some embodiments, the process conditions can preserve orsubstantially preserve Si—C bonds and, if present, Si—O and Si—N bondsin the as-deposited layer of the silicon carbide film 101. Accordingly,the reaction conditions adjacent to the substrate 100 provide for theselective breaking of Si—H and/or Si—Si bonds, e.g., extracting hydrogenfrom the broken Si—H bonds, but the reaction conditions do not providefor extracting oxygen from Si—O bonds, nitrogen from Si—N bonds, orcarbon from Si—C bonds. However, introduction of a co-reactant such asoxygen may extract carbon from Si—C bonds. It will be understood thatother reaction mechanisms may be taking place at the environmentadjacent to the substrate surface, including reaction mechanisms thatare less kinetically favorable such as substitution reactions.Generally, the described reaction conditions exist at the exposed faceof the substrate 100 (the face where the silicon carbide film 101 isdeposited). They may further exist at some distance above the substrate100, e.g., about 0.5 micrometers to about 150 millimeters above thesubstrate 100. In effect, activation of the precursor can happen in thegas phase at a substantial distance above the substrate 100. Typically,the pertinent reaction conditions will be uniform or substantiallyuniform over the entire exposed face of the substrate 100, althoughcertain applications may permit some variation.

In addition to silicon-containing precursors, the environment adjacentthe work piece (e.g., substrate 100) can include one or more radicalspecies, preferably in a substantially low energy state. An example ofsuch species includes hydrogen radicals (i.e., hydrogen atom radicals).In some embodiments, all, or substantially all, or a substantialfraction of the hydrogen atom radicals can be in the ground state, e.g.,at least about 90% or 95% of the hydrogen atom radicals adjacent thework piece are in the ground state. In certain embodiments, source gasis provided in a carrier gas such as helium. As an example, hydrogen gasmay be provided in a helium carrier at a concentration of about 1-10%hydrogen. Pressure, fraction of carrier gas such as helium, and otherprocess conditions are chosen so that the hydrogen atoms encounter thesubstrate 100 as radicals in a low energy state without recombining.

As explained elsewhere, hydrogen gas may be supplied into a remoteplasma source to generate hydrogen atom radicals. The remote plasmasource may be positioned upstream from the substrate surface and theenvironment adjacent to the substrate surface. Once generated, thehydrogen atom radicals may be in an excited energy state. For example,hydrogen in an excited energy state can have an energy of at least 10.2eV (first excited state). Excited hydrogen atom radicals may causeunselective decomposition of a silicon-containing precursor. Forexample, hydrogen atom radicals in an excited state can easily breakSi—H, Si—Si, Si—N, Si—O, and Si—C bonds, which can alter the compositionor physical or electrical characteristics of the silicon carbide film101. In some implementations, when the excited hydrogen atom radicalslose their energy, or relax, the excited hydrogen atom radical maybecome a substantially low energy state hydrogen atom radical or aground state hydrogen atom radical. Hydrogen atom radicals in asubstantially low energy state or ground state can be capable ofselectively breaking Si—H and Si—Si bonds while generally preservingSi—O, Si—N, and Si—C bonds. In some implementations, process conditionsmay be provided so that excited hydrogen atom radicals lose energy orrelax to form substantially low energy state or ground state hydrogenatom radicals. For example, the remote plasma source or associatedcomponents may be designed so that a residence time of hydrogen atomradicals diffusing from the remote plasma source to the substrate 100 isgreater than the energetic relaxation time of an excited hydrogen atomradical. The energetic relaxation time for an excited hydrogen atomradical can be about equal to or less than about 1×10⁻³ seconds.

A state in which a substantial fraction of hydrogen atom radicals are inthe ground state can be achieved by various techniques. Someapparatuses, such as described below, are designed to achieve thisstate. Apparatus features and process control features can be tested andtuned to produce a mild state in which a substantial fraction of thehydrogen atom radicals are in the ground state. For example, anapparatus may be operated and tested for charged particles downstream ofthe plasma source; i.e., near the substrate 100. The process andapparatus may be tuned until substantially no charged species exist nearthe substrate 100. Additionally, apparatus and process features may betuned to a configuration where they begin to produce a silicon carbidefilm 101 from a standard silicon-containing precursor. The relativelymild conditions that support such film deposition are chosen.

Other examples of radical species include oxygen-containing species suchas elemental oxygen radicals (atomic or diatomic), nitrogen-containingspecies such as elemental nitrogen radicals (atomic or diatomic), andN—H containing radicals such as ammonia radicals, where nitrogen isoptionally incorporated into the film. Examples of N—H containingradicals include but are not limited to radicals of methylamine,dimethylamine, and aniline. The aforementioned radical species may beproduced from a source gas that includes hydrogen, nitrogen, N—Hcontaining species, or mixtures thereof. In some embodiments,substantially all or a substantial fraction of atoms of the depositedfilm are provided by the precursor molecules. In such cases, the lowenergy radicals used to drive the deposition reaction may be exclusivelyhydrogen or other species that does not substantially contribute to themass of the deposited layer. In some embodiments, as discussed infurther detail below, the radical species can be produced by a remoteplasma source. In some embodiments, some radicals of higher energy stateor even ions can potentially be present near the wafer plane.

In some embodiments, the process conditions employ radical species in asubstantially low energy state sufficient to break Si—H bonds and/orSi—Si bonds while substantially preserving Si—O, Si—N, and Si—C bonds.Such process conditions may not have substantial amounts of ions,electrons, or radical species in high energy states such as states abovethe ground state. In some embodiments, the concentration of ions in theregion adjacent the film is no greater than about 10⁷/cm³. The presenceof substantial amounts of ions or high energy radicals may tend to breakSi—O, Si—N, and Si—C bonds, which can produce films with undesirableelectrical properties (e.g., high dielectric constants and/or lowbreakdown voltages) and poor conformality. It is believed that anexcessively reactive environment produces reactive precursor fragmentsthat have high sticking coefficients (representing a propensity tochemically or physically stick to work piece sidewalls), resulting inpoor conformality.

The silicon-containing precursors are typically delivered with otherspecies, notably carrier gas, in the environment adjacent to thesubstrate 100. In some implementations, the silicon-containingprecursors are present with the radical species and other species,including other reactive species and/or carrier gases. In someembodiments, the silicon-containing precursors may be introduced as amixture. Upstream from the deposition reaction surface, thesilicon-containing precursors can be mixed with an inert carrier gas.Example inert carrier gases include, but are not limited to, argon (Ar)and helium (He). In addition, the silicon-containing precursors can beintroduced in a mixture having major and minor species, with the minorspecies containing some element or structural feature (e.g., a ringstructure, a cage structure, an unsaturated bond, etc.) that is presentin the silicon carbide film 101 at a relatively low concentration. Itwill be understood, however, that the minor species may notsignificantly contribute to the composition or structural feature of thesilicon carbide film 101. The multiple precursors may be present inequimolar or relatively similar proportions as appropriate to form theprimary backbone or matrix in the resulting silicon carbide film 101. Inother embodiments, the relative amounts of the different precursors aresubstantially skewed from equimolarity.

In some embodiments, one or more silicon-containing precursors provideessentially all of the mass of the deposited silicon carbide film 101,with small amounts of hydrogen or other element from a remote plasmaproviding less than about 5% atomic or less than about 2% atomic of thefilm mass. In some embodiments, only the radical species and the one ormore silicon-containing precursors contribute to the composition of thedeposited silicon carbide film 101. In other embodiments, the depositionreaction includes a co-reactant other than one or moresilicon-containing precursors and the radical species, which may or maynot contribute to the composition of the deposited silicon carbide film101. Examples of such co-reactants include carbon dioxide (CO₂), carbonmonoxide (CO), water (H₂O), methanol (CH₃OH), oxygen (O₂), ozone (O₃),nitrogen (N₂), nitrous oxide (N₂O), ammonia (NH₃), diazene (N₂H₂),methane (CH₄), ethane (C₂H₆), acetylene (C₂H₂), ethylene (C₂H₄),diborane (B₂H₆), and combinations thereof. Such materials may be used asnitriding agents, oxidizers, reductants, etc. In some cases, they can beused to tune the amount of carbon in the deposited film by removing oradding a fraction of the carbon provided with the silicon-containingprecursor. In some implementations employing a non-hydrogen co-reactant,the co-reactant is introduced to the reaction chamber via the same flowpath as the silicon-containing precursor; e.g., a path including a gasoutlet or showerhead, typically without direct exposure to plasma. Insome embodiments, oxygen and/or carbon dioxide is introduced with theprecursor to alter the composition of the silicon carbide film 101 byremoving carbon from the film or precursor during deposition. In someimplementations employing a non-hydrogen co-reactant, the co-reactant isintroduced to the reaction chamber via the same flow path as thehydrogen, such that the co-reactant is at least partially converted toradicals and/or ions. In such implementations, the hydrogen radicals andthe co-reactant radicals both react with the silicon-containingprecursor(s) to produce the deposited silicon carbide film 101.

In certain embodiments where co-reactants are used and they areintroduced to the chamber with the species being converted to radicals(e.g., hydrogen), they may be provided to the reaction chamber inrelatively small amounts in comparison to the other gases in thereaction chamber, including the source of radicals (e.g., hydrogen) andany carrier gas(es) such as helium. For example, the co-reactant may bepresent in the process gases at about 0.05% or less by mass, or at about0.01% or less by mass, or at about 0.001% or less by mass. For example,a reactant mixture (that goes into the plasma source) may be about 10-20liters per minute (L/m) He, about 200-500 standard cubic centimeters perminute (sccm) H2, and about 1-10 sccm oxygen. However, it will beunderstood that in some implementations, the co-reactant may be presentin the process gases at about 0.05% or more by mass, or at about 1% ormore by mass, or at about 20% or more by mass. When the co-reactants areintroduced to the reaction chamber along with the silicon-containingprecursor (e.g., through a gas outlet or showerhead), they may bepresent at a higher concentration; for example about 2% or less or about0.1% or less by mass. When the co-reactant is a relatively weak reactant(e.g., a weak oxidant such as carbon dioxide), it may be present at evenhigher concentrations, such as about 10% or less or about 4% or less bymass. When the co-reactant is an additive, it may be present at evenhigher concentrations, such as about 10% or more or 20% or more by mass.

The temperature in the environment adjacent to the substrate 100 can beany suitable temperature facilitating the deposition reaction, butsometimes limited by the application of the device containing thesilicon carbide film 101. In some embodiments, the temperature in theenvironment adjacent to the substrate 100 can be largely controlled bythe temperature of a pedestal on which a substrate 100 is supportedduring deposition of the silicon carbide film 101. In some embodiments,the operating temperature can be between about 50° C. and about 500° C.For example, the operating temperature can be between about 250° C. andabout 400° C. in many integrated circuit applications. In someembodiments, increasing the temperature can lead to increasedcross-linking on the substrate surface.

The pressure in the environment adjacent to the substrate 100 can be anysuitable pressure to produce reactive radicals in a reaction chamber. Insome embodiments, the pressure can be about 35 Torr or lower. Forexample, the pressure can be between about 10 Torr and about 20 Torr,such as in embodiments implementing a microwave generated plasma. Inother examples, the pressure can be less than about 5 Torr, or betweenabout 0.2 Torr and about 5 Torr, such as in embodiments implementing aradio-frequency (RF) generated plasma.

The environment adjacent to the substrate 100 provides for deposition ofthe silicon carbide film 101 on the substrate 100 by remote plasma CVD.A source gas is supplied to a remote plasma source, and power isprovided to the remote plasma source that may cause the source gas todissociate and generate ions and radicals in an excited energy state.After excitation, the radicals in the excited energy state relax tosubstantially low energy state radicals or ground state radicals, suchas ground state hydrogen radicals. Bonds in the silicon-containingprecursor may be selectively broken by the hydrogen radicals in arelaxed energy state. Bonds in the co-reactant or additional precursormay be selectively broken by the hydrogen radicals in a relaxed energystate to activate the co-reactant or additional precursor.

Silicon carbide films are frequently used in semiconductor devices. Forexample, doped or undoped silicon carbide films may be employed as metaldiffusion barriers, etch stop layers, hard mask layers, gate spacers forsource and drain implants, encapsulation barriers for magnetoresistiverandom-access memory (MRAM) or resistive random-access memory (RRAM),and hermetic diffusion barriers at air gaps, among other applications.FIGS. 1B-1E illustrate cross-sections of structures containing siliconcarbide films in a variety of applications. FIG. 1B illustrates siliconcarbide thin film conformally deposited on features of a substrate. FIG.1C illustrates silicon carbide vertical structures on the sidewalls of agate electrode structure of a transistor. FIG. 1D illustrates siliconcarbide vertical structures on exposed sidewalls of copper lines in anair gap type metallization layer. FIG. 1E illustrates silicon carbidepore sealants for porous dielectric materials. Each of theseapplications is discussed in further detail below.

Chemical Structure of Precursors

As discussed, the precursors employed in forming silicon carbide filmscan include silicon-containing precursors, with at least some of thesilicon-containing precursors having at least one Si—H and/or at leastone Si—Si bond. In certain embodiments, the silicon-containing precursorhas at most one hydrogen atom on every silicon atom. Thus, for example,a precursor having one silicon atom has at most one hydrogen atom bondedto the silicon atom; a precursor having two silicon atoms has onehydrogen atom bonded to one silicon atom and optionally another hydrogenatom bonded to the second silicon atom; a precursor having three siliconatoms has at least one hydrogen atom bonded to one silicon atom andoptionally one or two more hydrogen atoms bonded to one or two of theremaining silicon atoms, and so on. In addition, the silicon-containingprecursors may include at least one Si—O bond, at least one Si—N bond,and/or at least one Si—C bond. While any number of appropriateprecursors can be used in forming silicon carbide films, at least someof the precursors will include silicon-containing precursors with atleast one Si—H bond or Si—Si bond, and optionally at least one Si—Obond, Si—N bond, and/or Si—C bond. In various implementations, thesilicon-containing precursor(s) contain no O—C or N—C bonds; e.g., theprecursor(s) contain no alkoxy (—O—R), where R is an organic group suchas a hydrocarbon group, or amine (—NR₁R₂) groups, wherein R₁ and R₂ areindependently hydrogen or organic groups. It is believed that suchgroups may impart high sticking coefficients to the precursors orfragments on which they reside.

In certain embodiments, some of the carbon provided for in the siliconcarbide film may be provided by one or more hydrocarbon moieties on thesilicon-containing precursor. Such moieties may be from alkyl groups,alkene groups, alkyne groups, aryl groups, and the like. In certainembodiments, the hydrocarbon group has a single carbon atom to minimizesteric hindrance of the Si—H and/or Si—Si bond breaking reaction duringdeposition. However, the precursors are not limited to single-carbongroups; higher numbers of carbon atoms may be used such as 2, 3, 4, 5,or 6 carbon atoms. In certain embodiments, the hydrocarbon group islinear. In certain embodiments, the hydrocarbon group is cyclic.

In certain embodiments, some of the carbon provided for in the siliconcarbide film may be provided by one or more hydrocarbon molecules in acarbon-containing precursor. Such hydrocarbon molecules may includecarbon-to-carbon chains, where a number of carbon atoms may be used suchas 2, 3, 4, 5, 6, or 7 carbon atoms. In some implementations, thehydrocarbon molecules include one or more carbon double bonds and/orcarbon triple bonds.

In some embodiments, the silicon-containing precursor falls into achemical class. It will be understood that other chemical classes ofsilicon-containing precursors may be employed and that thesilicon-containing precursors are not limited to the chemical classesdiscussed below.

In some embodiments, the silicon-containing precursor can be a siloxane.In some embodiments, the siloxane may be cyclic. Cyclic siloxanes mayinclude cyclotetrasiloxanes, such as2,4,6,8-tetramethylcyclotetrasiloxane (TMCTS),octamethylcyclotetrasiloxane (OMCTS), and heptamethylcyclotetrasiloxane(HMCTS). Other cyclic siloxanes can also include but are not limited tocyclotrisiloxanes and cyclopentasiloxanes. Embodiments using cyclicsiloxanes are ring structures that can introduce porosity into a siliconcarbide film, with the size of the pores corresponding to the radius ofthe ring. For example, a cyclotetrasiloxane ring can have a radius ofabout 6.7 Å.

In some embodiments, the siloxane may have a three-dimensional or cagedstructure. FIG. 2 illustrates examples of representative caged siloxaneprecursors. Caged siloxanes have silicon atoms bridged to one anothervia oxygen atoms to form a polyhedron or any 3-D structure. An exampleof a caged siloxane precursor molecule is silsesquioxane. Caged siloxanestructures are described in further detail in commonly owned U.S. Pat.No. 6,576,345 to Cleemput et al., which is incorporated by referenceherein in its entirety and for all purposes. Like the cyclic siloxanes,the caged siloxane can introduce porosity into a silicon carbide film.In some embodiments, the porosity scale is mesoporous.

In some embodiments, the siloxane may be linear. Examples of suitablelinear siloxanes include but are not limited to disiloxanes, such aspentamethyldisiloxane (PMDSO) and tetramethyldisiloxane (TMDSO), andtrisiloxanes such as hexamethyltrisiloxane, heptamethyltrisiloxane.

In some embodiments, the silicon-containing precursor can be an alkylsilane or other hydrocarbon-substituted silane. The alkyl silanesinclude a central silicon atom with one or more alkyl groups bonded toit as well as one or more hydrogen atoms bonded to it. In certainembodiments, any one or more of the alkyl groups contain 1-5 carbonatoms. The hydrocarbon groups may be saturated or unsaturated (e.g.,alkene (e.g., vinyl), alkyne, and aromatic groups). Examples include butare not limited to trimethylsilane (3MS), triethylsilane, pentamethyldisilamethane ((CH₃)₂Si—CH₂—Si(CH₃)₃), and dimethylsilane (2MS).

In some embodiments, the silicon-containing precursor can be an alkoxysilane. However, in some embodiments, it may be understood that thesilicon-containing precursor is not an alkoxy silane to avoid thepresence of alkoxy groups. Alkoxy silanes include a central silicon atomwith one or more alkoxy groups bonded it and one or more hydrogen atomsbonded to it. Examples include but are not limited to trimethoxysilane(TMOS), dimethoxysilane (DMOS), methoxysilane (MOS),methyldimethoxysilane (MDMOS), diethyoxymethylsilane (DEMS),dimethylethoxysilane (DMES), and dimethylmethoxysilane (DMMOS).

Disilanes, trisilanes, or other higher silanes may be used in place ofmonosilanes. An example of one such disilane from the alkyl silane classis hexamethyldisilane (HMDS). Another example of a disilane from thealkyl silane class can include pentamethyldisilane (PMDS). Other typesof alkyl silanes can include alkylcarbosilanes, which can have abranched polymeric structure with a carbon bonded to a silicon atom aswell as alkyl groups bonded to a silicon atom. Examples include dimethyltrimethylsilyl methane (DTMSM) and bis-dimethylsilyl ethane (BDMSE). Insome embodiments, one of the silicon atoms can have a carbon-containingor hydrocarbon-containing group attached to it, and one of the siliconatoms can have a hydrogen atom attached to it.

In some embodiments, the silicon-containing precursor can be anitrogen-containing compound such as a silicon-nitrogen hydride (e.g., asilazane). Generally, such compounds contain carbon, but only bonded tosilicon atoms, and not to nitrogen atoms. In certain embodiments, thenitrogen-containing compound does not have any carbon-nitrogen bonds. Incertain embodiments, the nitrogen-containing compound does not have anyamine moieties (—C—NR₁R₂), where R₁ and R₂ are the same or differentgroups such hydrogen atoms and hydrocarbon groups such as alkyl groups,alkene groups, or alkyne groups. Examples of suitable silicon-nitrogenprecursors include various silazanes such as cyclic and linear silazanescontaining one or more hydrocarbon moieties bonded to one or moresilicon atoms and one or more hydrogen atoms bonded to one or moresilicon atoms. Examples of silazanes include methyl-substituteddisilazanes and trisilazanes, such as tetramethyldisilazane andhexamethyl trisilazane.

In depositing silicon carbide, multiple silicon-containing precursorscan be present in the process gas. For example, a siloxane and an alkylsilane may be used together, or a siloxane and an alkoxy silane may beused together. The relative proportions of the individual precursors canbe chosen based on the chemical structures of precursors chosen and theapplication of the resulting silicon carbide film. For example, theamount of siloxane can be greater than the amount of silane in molarpercentages to produce a porous film as discussed in more detail below.

For depositing oxygen doped silicon carbide films, examples of suitableprecursors can include cyclic siloxanes such as cyclotetrasiloxanes suchas heptamethylcyclotetrasiloxane (HMCTS) andtetramethylcyclotetrasiloxane. Other cyclic siloxanes can also includebut are not limited to cyclotrisiloxanes and cyclopentasiloxanes. Fordepositing oxygen doped silicon carbide films, other examples ofsuitable precursors include linear siloxanes such as, but not limitedto, disiloxanes, such as pentamethyldisiloxane (PMDSO),tetramethyldisiloxane (TMDSO), hexamethyl trisiloxane, and heptamethyltrisiloxane.

For depositing undoped silicon carbide films, examples of suitableprecursors can include monosilanes substituted with one or more alkyl,alkene, and/or alkyne groups containing, e.g., 1-5 carbon atoms.Examples include but are not limited to trimethylsilane (3MS),dimethylsilane (2MS), triethylsilane (TES), andpentamethyldisilamethane. Additionally, disilanes, trisilanes, or otherhigher silanes may be used in place of monosilanes. Examples ofdisilanes can include hexamethyldisilane (HMDS) and pentamethyldisilane(PMDS). Other types of alkyl silanes can include alkylcarbosilanes.Examples include dimethyl trimethylsilyl methane (DTMSM) andbis-dimethylsilyl ethane (BDMSE).

For depositing nitrogen doped silicon carbide films, examples ofsuitable precursors can include silazanes, e.g., alkyldisilazanes andpossibly compounds including amino (—NH2) and alkyl groups separatelybonded to one or more silicon atoms. Alkyldisilazanes include silizanesand alkyl groups bonded to two silicon atoms. An example includes1,1,3,3-tetramethyldisilazane (TMDSN).

As explained, silicon-containing precursors are chosen to provide highlyconformal silicon carbide films. It is believed that silicon-containingprecursors having low sticking coefficients are capable of producinghighly conformal films. “Sticking coefficient” is a term used todescribe the ratio of the number of adsorbate species (e.g., fragmentsor molecules) that adsorb/stick to a surface compared to the totalnumber of species that impinge upon that surface during the same periodof time. The symbol S_(c) is sometimes used to refer to the stickingcoefficient. The value of S_(c) is between 0 (meaning that none of thespecies stick) and 1 (meaning that all of the impinging species stick).Various factors affect the sticking coefficient including the type ofimpinging species, surface temperature, surface coverage, structuraldetails of the surface, and the kinetic energy of the impinging species.Certain species are inherently more “sticky” than others, making themmore likely to adsorb onto a surface each time the specie impinges onthe surface. These more sticky species have greater stickingcoefficients (all other factors being equal), and are more likely toadsorb near the entrance of a recessed feature compared to less stickyspecies having lower sticking coefficients. In some cases, the stickingcoefficient of the precursors (at the relevant deposition conditions)may be about 0.05 or less, for example about 0.001 or less.

Apparatus

One aspect of the disclosure is an apparatus configured to accomplishthe methods described herein. A suitable apparatus includes hardware foraccomplishing the process operations and a system controller havinginstructions for controlling process operations in accordance with thepresent disclosure. In some embodiments, the apparatus for performingthe aforementioned process operations can include a remote plasmasource. A remote plasma source provides mild reaction conditions incomparison to a direct plasma. An example of a suitable remote plasmaapparatus is described in U.S. patent application Ser. No. 14/062,648,filed Oct. 24, 2013, which is incorporated herein by reference in itsentirety and for all purposes.

FIG. 3 presents a schematic diagram of a remote plasma apparatusaccording to certain embodiments. The device 300 includes a reactionchamber 310 with a showerhead 320. Inside the reaction chamber 310, asubstrate 330 rests on a stage or pedestal 335. In some embodiments, thepedestal 335 can be fitted with a heating/cooling element. A controller340 may be connected to the components of the device 300 to control theoperation of the device 300. For example, the controller 340 may containinstructions for controlling process conditions for the operations ofthe device 300, such as the temperature process conditions and/or thepressure process conditions. In some embodiments, the controller 340 maycontain instructions for controlling the flow rates of precursor gas,co-reactant gas, source gas, and carrier gas. The controller 340 maycontain instructions for changing the flow rate of the co-reactant gasover time. In addition or in the alternative, the controller 340 maycontain instructions for changing the flow rate of the precursor gasover time. A more detailed description of the controller 340 is providedbelow.

During operation, gases or gas mixtures are introduced into the reactionchamber 310 via one or more gas inlets coupled to the reaction chamber310. In some embodiments, two or more gas inlets are coupled to thereaction chamber 310. A first gas inlet 355 can be coupled to thereaction chamber 310 and connected to a vessel 350, and a second gasinlet 365 can be coupled to the reaction chamber 310 and connected to aremote plasma source 360. In embodiments including remote plasmaconfigurations, the delivery lines for the precursors and the radicalspecies generated in the remote plasma source are separated. Hence, theprecursors and the radical species do not substantially interact beforereaching the substrate 330. It will be understood that in someimplementations the gas lines may be reversed so that the vessel 350 mayprovide precursor gas flow through the second gas inlet 365 and theremote plasma source 360 may provide ions and radicals through the firstgas inlet 355.

One or more radical species may be generated in the remote plasma source360 and configured to enter the reaction chamber 310 via the second gasinlet 365. Any type of plasma source may be used in remote plasma source360 to create the radical species. This includes, but is not limited to,capacitively coupled plasmas, inductively coupled plasmas, microwaveplasmas, DC plasmas, and laser-created plasmas. An example of acapacitively coupled plasma can be a radio frequency (RF) plasma. Ahigh-frequency plasma can be configured to operate at 13.56 MHz orhigher. An example of such a remote plasma source 360 can be the GAMMA®,manufactured by Lam Research Corporation of Fremont, Calif. Anotherexample of such a RF remote plasma source 360 can be the Astron®,manufactured by MKS Instruments of Wilmington, Mass., which can beoperated at 440 kHz and can be provided as a subunit bolted onto alarger apparatus for processing one or more substrates in parallel. Insome embodiments, a microwave plasma can be used as the remote plasmasource 360, such as the Astex®, also manufactured by MKS Instruments. Amicrowave plasma can be configured to operate at a frequency of 2.45GHz. Gas provided to the remote plasma source may include hydrogen,nitrogen, oxygen, and other gases as mentioned elsewhere herein. Incertain embodiments, hydrogen is provided in a carrier such helium. Asan example, hydrogen gas may be provided in a helium carrier at aconcentration of about 1-10% hydrogen.

The precursors can be provided in vessel 350 and can be supplied to theshowerhead 320 via the first gas inlet 355. The showerhead 320distributes the precursors into the reaction chamber 310 toward thesubstrate 330. The substrate 330 can be located beneath the showerhead320. It will be appreciated that the showerhead 320 can have anysuitable shape, and may have any number and arrangement of ports fordistributing gases to the substrate 330. The precursors can be suppliedto the showerhead 320 and ultimately to the substrate 330 at acontrolled flow rate.

The one or more radical species formed in the remote plasma source 360can be carried in the gas phase toward the substrate 330. The one ormore radical species can flow through a second gas inlet 365 into thereaction chamber 310. It will be understood that the second gas inlet365 need not be transverse to the surface of the substrate 330 asillustrated in FIG. 3. In certain embodiments, the second gas inlet 365can be directly above the substrate 330 or in other locations. Thedistance between the remote plasma source 360 and the reaction chamber310 can be configured to provide mild reactive conditions such that theionized species generated in the remote plasma source 360 aresubstantially neutralized, but at least some radical species insubstantially low energy states remain in the environment adjacent tothe substrate 330. Such low energy state radical species are notrecombined to form stable compounds. The distance between the remoteplasma source 360 and the reaction chamber 310 can be a function of theaggressiveness of the plasma (e.g., determined in part by the source RFpower level), the density of gas in the plasma (e.g., if there's a highconcentration of hydrogen atoms, a significant fraction of them mayrecombine to form H₂ before reaching the reaction chamber 310), andother factors. In some embodiments, the distance between the remoteplasma source 360 and the reaction chamber 310 can be between about 1 cmand 30 cm, such as about 5 cm or about 15 cm.

In some embodiments, a co-reactant, which is not the primarysilicon-containing precursor or a hydrogen radical, is introduced duringthe deposition reaction. In some implementations, the apparatus isconfigured to introduce the co-reactant through the second gas inlet365, in which case the co-reactant is at least partially converted toplasma. In some implementations, the apparatus is configured tointroduce the co-reactant through the showerhead 320 via the first gasinlet 355. Examples of the co-reactant include oxygen, nitrogen,ammonia, carbon dioxide, carbon monoxide, and the like. The flow rate ofthe co-reactant can vary over time to produce a composition gradient ina graded film.

FIG. 4 illustrates a schematic diagram of an example plasma processingapparatus with a remote plasma source according to some otherimplementations. The plasma processing apparatus 400 includes the remoteplasma source 402 separated from a reaction chamber 404. The remoteplasma source 402 is fluidly coupled with the reaction chamber 404 via amultiport gas distributor 406, which may also be referred to as ashowerhead. Radical species are generated in the remote plasma source402 and supplied to the reaction chamber 404. One or moresilicon-containing precursors are supplied to the reaction chamber 404downstream from the remote plasma source 402 and from the multiport gasdistributor 406. The one or more silicon-containing precursors reactwith the radical species in a chemical vapor deposition zone 408 of thereaction chamber 404 to deposit a silicon carbide film on a surface of asubstrate 412. The chemical vapor deposition zone 408 includes anenvironment adjacent to the surface of the substrate 412.

The substrate 412 is supported on a substrate support or pedestal 414.The pedestal 414 may move within the reaction chamber 404 to positionthe substrate 412 within the chemical vapor deposition zone 408. In theembodiment shown in FIG. 4, pedestal 414 is shown having elevated thesubstrate 410 within the chemical vapor deposition zone 408. Thepedestal 414 may also adjust the temperature of the substrate 412 insome embodiments, which can provide some selective control overthermally activated surface reactions on the substrate 412.

FIG. 4 shows a coil 418 arranged around the remote plasma source 402,where the remote plasma source 402 includes an outer wall (e.g., quartzdome). The coil 418 is electrically coupled to a plasma generatorcontroller 422, which may be used to form and sustain plasma within aplasma region 424 via inductively coupled plasma generation. In someimplementations, the plasma generator controller 422 may include a powersupply for supplying power to the coil 418, where the power can be in arange between about 1 and 6 kilowatts (kW) during plasma generation. Insome implementations, electrodes or antenna for parallel plate orcapacitively coupled plasma generation may be used to generate acontinuous supply of radicals via plasma excitation rather thaninductively coupled plasma generation. Regardless of the mechanism usedto ignite and sustain the plasma in the plasma region 424, radicalspecies may continuously be generated using plasma excitation duringfilm deposition. In some implementations, hydrogen radicals aregenerated under approximately steady-state conditions duringsteady-state film deposition, though transients may occur at thebeginning and end of film deposition.

A supply of hydrogen radicals may be continuously generated within theplasma region 424 while hydrogen gas or other source gas is beingsupplied to the remote plasma source 402. Excited hydrogen radicals maybe generated in the remote plasma source 402. If not re-excited orre-supplied with energy, or re-combined with other radicals, the excitedhydrogen radicals lose their energy, or relax. Thus, excited hydrogenradicals may relax to form hydrogen radicals in a substantially lowenergy state or ground state.

The hydrogen gas or other source gas may be diluted with one or moreadditional gases. These one or more additional gases may be supplied tothe remote plasma source 402. In some implementations, the hydrogen gasor other source gas is mixed with one or more additional gases to form agas mixture, where the one or more additional gases can include acarrier gas. Non-limiting examples of additional gases can includehelium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), andnitrogen (N₂). The one or more additional gases may support or stabilizesteady-state plasma conditions within the remote plasma source 402 oraid in transient plasma ignition or extinction processes. In someimplementations, diluting hydrogen gas or other source gas with helium,for example, may permit higher total pressures without concomitantplasma breakdown. Put another way, a dilute gas mixture of hydrogen gasand helium may permit higher total gas pressure without increasingplasma power to the remote plasma source 402. As shown in FIG. 4, asource gas supply 426 is fluidly coupled with the remote plasma source402 for supplying the hydrogen gas or source gas. In addition, anadditional gas supply 428 is fluidly coupled with the remote plasmasource 402 for supplying the one or more additional gases. The one ormore additional gases may also include a co-reactant gas as describedabove. While the embodiment in FIG. 4 depicts the gas mixture of thesource gas and the one or more additional gases being introduced throughseparate gas outlets, it will be understood that the gas mixture may beintroduced directly into the remote plasma source 402. That is, apre-mixed dilute gas mixture may be supplied to the remote plasma source402 through a single gas outlet.

Gases, such as excited hydrogen and helium radicals and relaxedgases/radicals, flow out of the remote plasma source 402 and into thereaction chamber 404 via multiport gas distributor 406. Gases within themultiport gas distributor 406 and within the reaction chamber 404 aregenerally not subject to continued plasma excitation therein. In someimplementations, the multiport gas distributor 406 includes an ionfilter and/or a photon filter. Filtering ions and/or photons may reducesubstrate damage, undesirable re-excitation of molecules, and/orselective breakdown or decomposition of silicon-containing precursorswithin the reaction chamber 404. Multiport gas distributor 406 may havea plurality of gas ports 434 to diffuse the flow of gases into thereaction chamber 404. In some implementations, the plurality of gasports 434 may be mutually spaced apart. In some implementations, theplurality of gas ports 434 may be arranged as an array of regularlyspaced apart channels or through-holes extending through a plateseparating the remote plasma source 402 and the reaction chamber 404.The plurality of gas ports 434 may smoothly disperse and diffuse exitingradicals from the remote plasma source 402 into the reaction chamber404.

Typical remote plasma sources are far removed from reaction vessels.Consequently, radical extinction and recombination, e.g., via wallcollision events, may reduce active species substantially. In contrast,in some implementations, dimensions for the plurality of gas ports 434may be configured in view of the mean free path or gas flow residencetime under typical processing conditions to aid the free passage ofradicals into the reaction chamber 404. In some implementations,openings for the plurality of gas ports 434 may occupy between about 5%and about 20% of an exposed surface area of the multiport gasdistributor 406. In some implementations, the plurality of gas ports 434may each have an axial length to diameter ratio of between about 3:1 and10:1 or between about 6:1 and about 8:1. Such aspect ratios may reducewall-collision frequency for radical species passing through theplurality of gas ports 434 while providing sufficient time for amajority of excited state radical species to relax to ground stateradical species. In some implementations, dimensions of the plurality ofgas ports 434 may be configured so that the residence time of gasespassing through the multiport gas distributor 406 is greater than thetypical energetic relaxation time of an excited state radical species.Excited state radical species for hydrogen source gas may be denoted by.H* in FIG. 4 and ground state radical species for hydrogen source gasmay be denoted by .H in FIG. 4.

In some implementations, excited state radical species exiting theplurality of gas ports 434 may flow into a relaxation zone 438 containedwithin an interior of the reaction chamber 404. The relaxation zone 438is positioned upstream of the chemical vapor deposition zone 408 butdownstream of the multiport gas distributor 406. Substantially all or atleast 90% of the excited state radical species exiting the multiport gasdistributor 406 will transition into relaxed state radical species inthe relaxation zone 438. Put another way, almost all of the excitedstate radical species (e.g., excited hydrogen radicals) entering therelaxation zone 438 become de-excited or transition into a relaxed stateradical species (e.g., ground state hydrogen radicals) before exitingthe relaxation zone 438. In some implementations, process conditions ora geometry of the relaxation zone 438 may be configured so that theresidence time of radical species flowing through the relaxation zone438, e.g., a time determined by mean free path and mean molecularvelocity, results in relaxed state radical species flowing out of therelaxation zone 438.

With the delivery of radical species to the relaxation zone 438 from themultiport gas distributor 406, one or more silicon-containing precursorsand/or one or more co-reactants may be introduced into the chemicalvapor deposition zone 408. The one or more silicon-containing precursorsmay be introduced via a gas distributor or gas outlet 442, where the gasoutlet 442 may be fluidly coupled with a precursor supply source 440.The relaxation zone 438 may be contained within a space between themultiport gas distributor 406 and the gas outlet 442. The gas outlet 442may include mutually spaced apart openings so that the flow of the oneor more silicon-containing precursors may be introduced in a directionparallel with gas mixture flowing from the relaxation zone 438. The gasoutlet 442 may be located downstream from the multiport gas distributor406 and the relaxation zone 438. The gas outlet 442 may be locatedupstream from the chemical vapor deposition zone 408 and the substrate412. The chemical vapor deposition zone 408 is located within theinterior of the reaction chamber 404 and between the gas outlet 442 andthe substrate 412.

Substantially all of the flow of the one or more silicon-containingprecursors may be prevented from mixing with excited state radicalspecies adjacent to the multiport gas distributor 406. Relaxed or groundstate radical species mix in a region adjacent to the substrate 412 withthe one or more silicon-containing precursors. The chemical vapordeposition zone 408 includes the region adjacent to the substrate 412where the relaxed or ground state radical species mix with the one ormore silicon-containing precursors. The relaxed or ground state radicalspecies mix with the one or more silicon-containing precursors in thegas phase during CVD formation of a silicon carbide film.

In some implementations, a co-reactant may be introduced from the gasoutlet 442 and flowed along with the one or more silicon-containingprecursors. The co-reactant may include a depositing additive or anon-depositing additive as described below. The co-reactant may beintroduced downstream from the remote plasma source 402. The co-reactantmay be supplied from the precursor supply source 440 or other source(not shown) fluidly coupled to the gas outlet 442. The co-reactant maybe a carbon-containing precursor or a second silicon-containingprecursor without Si—H or Si—Si bonds as described below. In someimplementations, a co-reactant may be introduced from the multiport gasdistributor 406 and flowed along with the radical species generated inthe remote plasma source 402 and into the reaction chamber 404. This mayinclude radicals and/or ions of a co-reactant gas provided in the remoteplasma source 402. The co-reactant may be supplied from the additionalgas supply 428.

The gas outlet 442 may be separated from the multiport gas distributor406 by a sufficient distance to prevent back diffusion or back streamingof the one or more silicon-containing precursors. In someimplementations, the gas outlet 442 may be separated from the pluralityof gas ports 434 by a distance between about 0.5 inches and about 5inches, or between about 1.5 inches and about 4.5 inches, or betweenabout 1.5 inches and about 3 inches.

Process gases may be removed from the reaction chamber 404 via an outlet448 configured that is fluidly coupled to a pump (not shown). Thus,excess silicon-containing precursors, co-reactants, radical species, anddiluent and displacement or purge gases may be removed from the reactionchamber 404. In some implementations, a system controller 450 is inoperative communication with the plasma processing apparatus 400. Insome implementations, the system controller 450 includes a processorsystem 452 (e.g., microprocessor) configured to execute instructionsheld in a data system 454 (e.g., memory). In some implementations, thesystem controller 450 may be in communication with the plasma generatorcontroller 422 to control plasma parameters and/or conditions. In someimplementations, the system controller 450 may be in communication withthe pedestal 414 to control pedestal elevation and temperature. In someimplementations, the system controller 450 may control other processingconditions, such as RF power settings, frequency settings, duty cycles,pulse times, pressure within the reaction chamber 404, pressure withinthe remote plasma source 402, gas flow rates from the source gas supply426 and the additional gas supply 428, gas flow rates from the precursorsupply source 440 and other sources, temperature of the pedestal 414,and temperature of the reaction chamber 404, among others.

Aspects of the controller 450 of FIG. 4 described below also apply tothe controller 340 of FIG. 3. The controller 450 may containinstructions for controlling process conditions for the operation of theplasma processing apparatus 400. The controller 450 will typicallyinclude one or more memory devices and one or more processors. Theprocessor may include a CPU or computer, analog and/or digitalinput/output connections, stepper motor controller boards, etc.Instructions for implementing appropriate control operations areexecuted on the processor. These instructions may be stored on thememory devices associated with the controller 450 or they may beprovided over a network.

In certain embodiments, the controller 450 controls all or mostactivities of the plasma processing apparatus 400 described herein. Forexample, the controller 450 may control all or most activities of theplasma processing apparatus 400 associated with depositing a siliconcarbide film and, optionally, other operations in a fabrication flowthat includes the silicon carbide film. The controller 450 may executesystem control software including sets of instructions for controllingthe timing, gas composition, gas flow rates, chamber pressure, chambertemperature, RF power levels, substrate position, and/or otherparameters. Other computer programs, scripts, or routines stored onmemory devices associated with the controller 450 may be employed insome embodiments. To provide relatively mild reactive conditions at theenvironment adjacent to the substrate 412, parameters such as the RFpower levels, gas flow rates to the plasma region 424, gas flow rates tothe chemical vapor deposition zone 408, and timing of the plasmaignition can be adjusted and maintained by controller 450. Additionally,adjusting the substrate position may further reduce the presence ofhigh-energy radical species at the environment adjacent to the substrate412. In a multi-station reactor, the controller 450 may comprisedifferent or identical instructions for different apparatus stations,thus allowing the apparatus stations to operate either independently orsynchronously.

In some embodiments, the controller 450 may include instructions forperforming operations such as flowing one or more silicon-containingprecursors through the gas outlet 442 into the reaction chamber 404,providing a source gas into the remote plasma source 402, generating oneor more radical species of the source gas in the remote plasma source402, introducing the one or more radical species in a substantially lowenergy state from the remote plasma source 402 into the reaction chamber404 to react with the one or more silicon-containing precursors todeposit a silicon carbide film on the substrate 412. The one or moreradical species in the reaction chamber 404 in an environment adjacentto the substrate 412 may be hydrogen radicals in a ground state. In someimplementations, the controller 450 may include instructions for flowinga co-reactant with the one or more silicon-containing precursors intothe reaction chamber 404. The co-reactant may include a non-depositingadditive or a depositing additive.

In some embodiments, the apparatus 400 may include a user interfaceassociated with controller 450. The user interface may include a displayscreen, graphical software displays of the apparatus 400 and/or processconditions, and user input devices such as pointing devices, keyboards,touch screens, microphones, etc.

The computer program code for controlling the above operations can bewritten in any conventional computer readable programming language: forexample, assembly language, C, C++, Pascal, Fortran, or others. Compiledobject code or script is executed by the processor to perform the tasksidentified in the program.

Signals for monitoring the process may be provided by analog and/ordigital input connections of the system controller. The signals forcontrolling the process are output on the analog and digital outputconnections of the processing system.

In general, the methods described herein can be performed on systemsincluding semiconductor processing equipment such as a processing toolor tools, chamber or chambers, a platform or platforms for processing,and/or specific processing components (a wafer pedestal, a gas flowsystem, etc.). These systems may be integrated with electronics forcontrolling their operation before, during, and after processing of asemiconductor wafer or substrate. In general, the electronics arereferred to as the controller, which may control various components orsubparts of the system or systems. The controller, depending on theprocessing requirements and/or the type of system, may be programmed tocontrol any of the processes disclosed herein, including the delivery ofprocessing gases, temperature settings (e.g., heating and/or cooling),pressure settings, vacuum settings, power settings, RF generatorsettings, RF matching circuit settings, frequency settings, flow ratesettings, fluid delivery settings, positional and operation settings,wafer transfers into and out of a tool and other transfer tools and/orload locks connected to or interfaced with a specific system.

Broadly speaking, the controller may be defined as electronics havingvarious integrated circuits, logic, memory, and/or software that receiveinstructions, issue instructions, control operation, enable cleaningoperations, enable endpoint measurements, and the like. The integratedcircuits may include chips in the form of firmware that store programinstructions, digital signal processors (DSPs), chips defined asapplication specific integrated circuits (ASICs), and/or one or moremicroprocessors, or microcontrollers that execute program instructions(e.g., software). Program instructions may be instructions communicatedto the controller in the form of various individual settings (or programfiles), defining operational parameters for carrying out a particularprocess on or for a semiconductor wafer or to a system. The operationalparameters may, in some embodiments, be part of a recipe defined byprocess engineers to accomplish one or more processing steps during thefabrication of one or more layers, materials (e.g., silicon carbide),surfaces, circuits, and/or dies of a wafer.

The controller, in some implementations, may be a part of or coupled toa computer that is integrated with, coupled to the system, otherwisenetworked to the system, or a combination thereof. For example, thecontroller may be in the “cloud” or all or a part of a fab host computersystem, which can allow for remote access of the wafer processing. Thecomputer may enable remote access to the system to monitor currentprogress of fabrication operations, examine a history of pastfabrication operations, examine trends or performance metrics from aplurality of fabrication operations, to change parameters of currentprocessing, to set processing steps to follow a current processing, orto start a new process. In some examples, a remote computer (e.g. aserver) can provide process recipes to a system over a network, whichmay include a local network or the Internet. The remote computer mayinclude a user interface that enables entry or programming of parametersand/or settings, which are then communicated to the system from theremote computer. In some examples, the controller receives instructionsin the form of data, which specify parameters for each of the processingsteps to be performed during one or more operations. It should beunderstood that the parameters may be specific to the type of process tobe performed and the type of tool that the controller is configured tointerface with or control. Thus as described above, the controller maybe distributed, such as by comprising one or more discrete controllersthat are networked together and working towards a common purpose, suchas the processes and controls described herein. An example of adistributed controller for such purposes would be one or more integratedcircuits on a chamber in communication with one or more integratedcircuits located remotely (such as at the platform level or as part of aremote computer) that combine to control a process on the chamber.

In addition to the silicon carbide deposition described herein, examplesystems may include a plasma etch chamber or module, a depositionchamber or module, a spin-rinse chamber or module, a metal platingchamber or module, a clean chamber or module, a bevel edge etch chamberor module, a physical vapor deposition (PVD) chamber or module, achemical vapor deposition (CVD) chamber or module, an atomic layerdeposition (ALD) chamber or module, an atomic layer etch (ALE) chamberor module, an ion implantation chamber or module, a track chamber ormodule, and any other semiconductor processing systems that may beassociated or used in the fabrication and/or manufacturing ofsemiconductor wafers.

As noted above, depending on the process step or steps to be performedby the tool, the controller might communicate with one or more of othertool circuits or modules, other tool components, cluster tools, othertool interfaces, adjacent tools, neighboring tools, tools locatedthroughout a factory, a main computer, another controller, or tools usedin material transport that bring containers of wafers to and from toollocations and/or load ports in a semiconductor manufacturing factory.

The apparatus/process described hereinabove may be used in conjunctionwith lithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallyincludes some or all of the following operations, each operation enabledwith a number of possible tools: (1) application of photoresist on aworkpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curingof photoresist using a hot plate or furnace or UV curing tool; (3)exposing the photoresist to visible or UV or x-ray light with a toolsuch as a wafer stepper; (4) developing the resist so as to selectivelyremove resist and thereby pattern it using a tool such as a wet bench;(5) transferring the resist pattern into an underlying film or workpieceby using a dry or plasma-assisted etching tool; and (6) removing theresist using a tool such as an RF or microwave plasma resist stripper.

Co-Reactants for Improving Step Coverage

ALD techniques are generally employed to achieve high step coverage,where step coverage can be equal to or greater than 90%, equal to orgreater than 95%, equal to or greater than 99%, or even 100%. However,deposition of silicon carbide films using ALD presents many challengesincluding thermodynamic challenges that can make ALD of silicon carbidefilms difficult to achieve. Moreover, the deposition rate of ALD isslower compared to typical CVD techniques and may not be desirable inmanufacturing processes. The present disclosure relates to deposition ofsilicon carbide film using remote plasma CVD. Doped or undoped siliconcarbide films may be deposited using a remote plasma CVD technique thatachieves step coverage comparable to ALD techniques.

As discussed above, the deposition reaction for depositing siliconcarbide films may include a co-reactant in addition to thesilicon-containing precursor and the radical species. Introduction ofthe co-reactant may serve to increase step coverage of the siliconcarbide film. The co-reactant may be flowed into a reaction chamberalong with the silicon-containing precursor, where the co-reactant maybe flowed downstream from a remote plasma source. For example, a gasoutlet for introducing the silicon-containing precursor and theco-reactant may be positioned downstream from the remote plasma source.The remote plasma source is considered upstream from the substrate andthe environment adjacent to the substrate. In some implementations, thegas outlet for introducing the silicon-containing precursor and theco-reactant may be positioned downstream from the remote plasma sourceand upstream from the substrate and the environment adjacent to thesubstrate.

In some implementations, the co-reactant may be a depositing additive ora non-depositing additive. As used herein, a non-depositing additive isan additive to the deposition reaction that would not otherwise depositon its own without the presence of a silicon-containing precursorparticipating in the remote plasma CVD reaction. A depositing additiveis an additive to the deposition reaction that would deposit on its owneven without the presence of a silicon-containing precursorparticipating in the remote plasma CVD reaction.

The non-depositing additive or the depositing additive may be introducedas a second precursor in addition to the silicon-containing precursor.The second precursor has a chemistry that serves to improve the stepcoverage of the silicon carbide film. Step coverage of the depositedsilicon carbide film may be measured with respect to one or morefeatures of the substrate. “Features” as used herein may refer to anon-planar structure on the substrate, typically a surface beingmodified in a semiconductor device fabrication operation. Examples offeatures include trenches, vias, pads, pillars, domes, and the like. Afeature typically has an aspect ratio (depth or height to width). Insome implementations, the step coverage of the silicon carbide film isat least 90%, at least 95%, or at least 99%.

Non-Depositing Additives

In some implementations, the non-depositing additive is a hydrocarbonmolecule. For example, the hydrocarbon molecule may be a small-chainhydrocarbon molecule with at least one double bond or at least onetriple bond. In some implementations, the hydrocarbon molecule includesa carbon chain between 3 carbon atoms and 7 carbon atoms. Thehydrocarbon molecule may include one or more unsaturated carbon bonds,such as one or more carbon-to-carbon double bonds or triple bonds. Thus,the hydrocarbon molecule may include an alkene or alkyne group. Examplesof suitable hydrocarbon molecules include propylene, ethylene, butene,pentene, butadiene, pentadiene (e.g., 1,4 pentadiene), hexadiene,hexadiene, heptadiene, toluene, and benzene. Additional examples ofsuitable hydrocarbon molecules include acetylene, propyne, butyne,pentyne (e.g., 1-pentyne), and hexyne (e.g., 2-hexyne). Thenon-depositing additive may also be referred to as a carbon-containingprecursor or non-depositing carbon-containing precursor.

The non-depositing additive is flowed along with one or moresilicon-containing precursors as described above. Each of thesilicon-containing precursors may include one or more Si—H bonds and/orSi—Si bonds. Furthermore, each of the silicon-containing precursors mayinclude or more Si—C bonds, Si—N, and/or Si—O bonds, no C—O bonds, andno C—N bonds. Examples of silicon-containing precursors may include butare not limited to alkylcarbosilanes, siloxanes, or a silazanes. Thenon-depositing additive may be introduced into the reaction chamberdownstream from one or more radical species. The radical species may begenerated in a remote plasma source upstream from the gas outlet forintroducing the non-depositing additive. The radical species may includehydrogen radicals, where the hydrogen radicals are in a substantiallylow energy state or ground state upon mixing or interacting with thenon-depositing additive.

Without being limited by any theory, hydrogen radicals in asubstantially low energy state or ground state may interact with thenon-depositing additive. It is believed that the hydrogen radicals inthe substantially low energy state or ground state may interact with thenon-depositing additive to form species that are unable to deposit atreasonable temperatures, such as greater than about 50° C. or greaterthan about 25° C. The hydrogen radicals may interact with alkyne oralkene groups in a hydrocarbon molecule of the non-depositing additiveto form activated alkanes (e.g., methane). In some instances, thehydrocarbon molecule breaks down into smaller-chain hydrocarbonmolecules or radicals. Such species may be too lightweight and may havetoo low of a sticking coefficient to deposit on its own. In other words,the non-depositing additive may serve as a passive spectator in thedeposition reaction without significantly contributing to thecomposition of the silicon carbide film. Without being limited by anytheory, the activated alkanes may interact with the silicon-containingprecursor to form a new species that has a lower sticking coefficientthan the original silicon-containing precursor. The hydrocarbon moleculeand byproducts of any reaction with hydrogen radicals in thesubstantially low energy state or ground state do not get incorporatedin the silicon carbide film in a substantial amount. As used herein, a“substantial amount” with respect to incorporation of an additive in thesilicon carbide film may refer to a change in atomic concentration ofcarbon or silicon by an amount equal to or greater than about 5%compared to deposition of the silicon carbide film without the additive.In some implementations, a percentage of C—C bonds in the siliconcarbide film is equal to or less than about 2%, equal to or less thanabout 1%, equal to or less than about 0.5%, or even 0%.

In some implementations, a flow rate of the non-depositing species canbe controlled. The flow rate of the non-depositing species can affectdeposition conditions such as deposition rate and step coverage of thesilicon carbide film. In some implementations, the flow rate of thenon-depositing species is between about 1 sccm and about 50 sccm, orbetween about 5 sccm and about 25 sccm.

FIG. 5A shows a TEM image of a silicon carbide thin film deposited onsubstrate features without using a carbon-containing non-depositingadditive. The silicon carbide film is deposited with a first precursorincluding a silicon-containing species but without a second precursorincluding a carbon-containing species. FIG. 5B shows a TEM image of asilicon carbide thin film deposited on substrate features using acarbon-containing non-depositing additive. The silicon carbide film isdeposited with a first precursor including a silicon-containing speciesand a second precursor including a carbon-containing species.

Table 1 summarizes differences in deposition of the silicon carbide filmbetween FIG. 5A and FIG. 5B with respect to step coverage. Introductionof a second precursor, particularly a carbon-containing precursor suchas propylene, significantly improves the step coverage of the siliconcarbide film. For example, the step coverage of the silicon carbide filmis at least 95% or at least 99%. Furthermore, a film composition of thesilicon carbide film is not significantly altered with introduction ofthe carbon-containing precursor. Film quality and film density are alsosubstantially preserved with the introduction of the carbon-containingprecursor. For example, the film density can be equal to or greater thanabout 2.0 g/cm³.

TABLE 1 Precursors: silicon-containing precursor and Precursors:carbon-containing silicon-containing precursor precursor (e.g.,propylene) Step Coverage 88.0% 100.0%

Depositing Additives

In some implementations, the depositing additive is a secondsilicon-containing precursor that is flowed along with a firstsilicon-containing precursor. The first silicon-containing precursor hasone or more Si—H bonds and/or Si—Si bonds. The second silicon-containingprecursor has no Si—H bonds and no Si—Si bonds. In some implementations,the second silicon-containing precursor has one or more Si—C bonds. Insome implementations, the second silicon-containing precursor is anorganosilicon precursor that includes an alkyl silane. Examples oforganosilicon precursors that include an alkyl silane without any Si—Hbonds or Si—Si bonds include but are not limited to tetramethylsilane(4MS), tetraethylsilane, tetrapropylsilane, andhexamethyldisilylpentane. In some implementations, the secondsilicon-containing precursor is an organosilicon precursor that includesa silazane. An example of an organosilicon precursor that includes asilazane without any Si—H bonds or Si—Si bonds includes but is notlimited to hexamethyldisilazane. In some implementations, the secondsilicon-containing precursor is an organosilicon precursor that includesan alkyl silyl group. An example of an organosilicon precursor thatincludes an alkyl silyl group without any Si—H bonds or Si—Si bondsincludes but is not limited to bistrimethylsilyl methane.

The depositing additive is flowed along with one or more firstsilicon-containing precursors as described above. Each of the firstsilicon-containing precursors may include one or more Si—H bonds and/orSi—Si bonds. Furthermore, each of the first silicon-containingprecursors may include or more Si—C bonds, Si—N, and/or Si—O bonds, noC—O bonds, and no C—N bonds. Examples of first silicon-containingprecursors may include but are not limited to alkylcarbosilanes,siloxanes, or a silazanes. The depositing additive may be introducedinto the reaction chamber downstream from one or more radical species.The radical species may be generated in a remote plasma source upstreamfrom the gas outlet for introducing the depositing additive. The radicalspecies may include hydrogen radicals, where the hydrogen radicals arein a substantially low energy state or ground state upon mixing orinteracting with the depositing additive (the second silicon-containingprecursor).

Without being limited by any theory, one of the more kineticallyfavorable reaction mechanisms in the deposition reaction includeshydrogen abstraction, which involves selective breaking of Si—H bonds inthe first silicon-containing precursor. One of the less kineticallyfavorable reaction mechanisms in the deposition reaction includeshydrogen substitution, which involves substitution of alkyl groups inthe second silicon-containing precursor with hydrogen. The substitutionresults in hydrocarbon radicals that may react with activated species ofthe first silicon-containing precursor. By increasing a partial pressureof the second silicon-containing precursor, a reaction equilibrium isincreased towards products of the hydrogen substitution reactionmechanism. It is believed that the hydrogen radicals in thesubstantially low energy state or ground state may interact with thedepositing additive to form species that are able to deposit regardlessof temperature, even for temperatures greater than about 50° C. orgreater than about 25° C. Interactions with the hydrogen radicals mayresult in activated first silicon-containing precursors and/or activatedsecond silicon-containing precursors (i.e., activated additivesilicon-containing precursors) that can react with each other. Withoutbeing limited by any theory, one potential mechanism involves the firstsilicon-containing precursor being activated by hydrogen radicals, andthe activated first silicon-containing precursor forming a silicon-basedradical that can react with the second silicon-containing precursor toform a new depositing species and hydrocarbon radical. This new specieswill have a lower sticking coefficient than the originalsilicon-containing precursor. Accordingly, the depositing additive doesnot serve as a passive spectator, but can significantly contribute tothe composition of the silicon carbide film. The depositing additive andbyproducts of any reaction with the hydrogen radicals in thesubstantially low energy state or ground state may get incorporated inthe silicon carbide film in a substantial amount.

In some implementations, a flow rate of the depositing species can becontrolled. The flow rate of the depositing species can affectdeposition conditions such as deposition rate and step coverage of thesilicon carbide film. In some implementations, the flow rate of thedepositing species is between about 25 sccm and about 200 sccm, orbetween about 50 sccm and about 100 sccm. In some implementations, theflow rate of the depositing species can be at least two times greaterthan a flow rate of the original silicon-containing precursor.

FIG. 6A shows a TEM image a silicon carbide thin film deposited onsubstrate features without using a silicon-containing depositingadditive. The silicon carbide film is deposited with a first precursorincluding a silicon-containing species having one or more Si—H and/orSi—Si bonds and without a second precursor including asilicon-containing species having no Si—H or Si—Si bonds. FIG. 6B showsa TEM image of a silicon carbide thin film deposited on substratefeatures using a silicon-containing depositing additive. The siliconcarbide film is deposited with a first precursor including asilicon-containing species having one or more Si—H and/or Si—Si bondsand with a second precursor including a silicon-containing specieshaving no Si—H or Si—Si bonds.

Table 2 summarizes differences in deposition of the silicon carbide filmbetween FIG. 6A and FIG. 6B with respect to step coverage. Introductionof a second precursor, particularly an organosilicon precursor with noSi—H or Si—Si bonds such as tetramethylsilane, significantly improvesthe step coverage of the silicon carbide film. For example, the stepcoverage of the silicon carbide film is at least 95% or at least 99%. Afilm composition of the silicon carbide film is slightly altered but notsignificantly altered with introduction of the second silicon-containingprecursor. Film quality and film density are also substantiallypreserved with the introduction of the carbon-containing precursor. Forexample, the film density can be equal to or greater than about 2.0g/cm³.

TABLE 2 Precursors: first silicon-containing Precursors: precursor andsecond first silicon- silicon-containing containing precursor precursor(e.g., tetramethylsilane) Step Coverage 85.8% 99.2%

Structure and Properties of the Deposited Film

The deposited film will include silicon, carbon, and in some casesoxygen, nitrogen, and/or one or more other elements. In someembodiments, the atomic concentration of silicon is between about 15%and 45% (or about 25% to 40%), the atomic concentration of carbon isbetween about 10% and 50%, the atomic concentration of oxygen is betweenabout 0% and 45%, and the atomic concentration of nitrogen is betweenabout 0% and 45%. In one example, the atomic concentration of silicon isabout 30%, the atomic concentration of oxygen is about 25%, and theatomic concentration of carbon is about 45%. In another example, theatomic concentration of silicon is about 30%, the atomic concentrationof oxygen is about 45%, and the atomic concentration of carbon is about25%. In another example, the film contains about 10-15% carbon and about30-40% oxygen, both on an atomic basis. In all cases, the film containssome hydrogen. However, it will be understood that the relative atomicconcentration of hydrogen will be small, e.g., equal to or less thanabout 5%. It will be understood that the relative atomic concentrationscan vary depending on the choice of the precursor. The silicon atomswill form bonds with carbon and optionally nitrogen and/or oxygen atoms.In some embodiments, the deposited film contains more Si—O bonds thanSi—C bonds. This can provide a relatively porous film with a lowerdielectric constant. In some examples, the deposited film contains aratio of Si—O bonds to Si—C bonds that is between about 0.5:1 and 3:1.In some embodiments, the deposited film contains more Si—N bonds thanSi—C bonds. In some examples, the deposited film contains a ratio ofSi—N bonds to Si—C bonds that is between about 0.5:1 and 3:1. In certainembodiments, the film density is between about 2 and 2.7 g/cm³.

In some embodiments, the internal structure of the precursor ismaintained in the deposited film. This structure may preserve all ormost of the Si—C, and Si—O and/or Si—N bonds, if present, in theprecursor, while linking or cross-linking individual precursor moietiesthrough bonds at locations where Si—H bonds and/or Si—Si bonds existedin the precursor molecules and/or through additional condensationreactions on the growing surface if sufficient thermal energy isprovided.

The process conditions described earlier herein can provide a filmstructure that is highly conformal. The relatively mild processconditions can minimize the degree of ion bombardment at the surface ofthe substrate so that the deposition lacks directionality. Moreover, therelatively mild process conditions can reduce the number of radicalswith high sticking coefficients that would have a tendency to stick tothe sidewalls of previously deposited layers or films. In certainembodiments, for an aspect ratio of about 2:1 to 10:1, the siliconcarbide film may be deposited with a conformality of between about 25%and 100%, more typically between about 50% and 100%, and even moretypically between about 80% and 100%. Conformality may be calculated bycomparing the average thickness of a deposited film on a bottom,sidewall, or top of a feature to the average thickness of a depositedfilm on a bottom, sidewall, or top of a feature. For example,conformality may be calculated by dividing the average thickness of thedeposited film on the sidewall by the average thickness of the depositedfilm at the top of the feature and multiplying it by 100 to obtain apercentage. For certain applications, a conformality of between about85% and 95% is sufficient. In some examples depositing silicon carbideon features having an aspect ratio of between about 2:1 and about 4:1,the conformality is at least about 90%. Certain BEOL (back end of line)processes fall into this category. In some examples depositing siliconcarbide on features having an aspect ratio of between about 4:1 andabout 6:1, the conformality is at least about 80%. Certain spacerdeposition processes fall into this category. In some examplesdepositing silicon carbide on features having an aspect ratio of betweenabout 7:1 and about 10:1 (and even higher), the conformality is at leastabout 90%. Certain DRAM (dynamic random access memory) fabricationprocesses fall into this category.

The process conditions can also provide a film structure with a highbreakdown voltage and a low leakage current. By introducing a limitedamount of oxygen or nitrogen into a SiC class of material, leakage pathsprovided by Si—H bonds and/or Si—CH₂—Si bonds may be blocked by oxygenor nitrogen. The mode of conduction may be different in Si—O and Si—N atlow fields. This can provide improved electrical properties whilemaintaining a relatively low dielectric constant. In variousembodiments, the film has an effective dielectric constant of about 5 orlower, or about 4.0 or lower, and in some cases about 3.5 or lower, andsome cases about 3.0 or lower, and in still other implementations about2.5 or lower. The effective dielectric constant can depend on thebonding and density. In certain embodiments, SiOC films are made with adielectric constant of 6 or greater, particularly when the carboncontent is relatively high. If leakage current is an importantconsideration, SiOC needs to be <5. The lower you go, the worse will beits hermetic and barrier and thermal resistance properties. In someembodiments, where applications demand low hermeticity and diffusionlimits, excellent etch resistance, thermal stability etc., the siliconcarbide film may be made dense and highly cross-linked. This can beaccomplished by, for example, a) depositing the film at a relativelyhigh temperature, and/or b) providing a relatively highradicals:precursor ratio. In some embodiments, the silicon carbide filmcan be relatively thin and yet serve as an effective hermetic ordiffusion barrier.

In some embodiments, the deposited film can be porous. As discussedearlier herein, the silicon-containing precursors can include cyclicsiloxanes and caged siloxanes. These precursors, and others that havesignificant interior open space, can introduce significant porosity intothe structure of the deposited film. Porosity in the deposited film canfurther lower the dielectric constant. In some embodiments, the porosityof the deposited silicon carbide film is between about 20% and 50%. Thepore size of porous film may track that of the cyclic or cagedprecursor. In certain embodiments, the film's average pore size isbetween about 5 Å and 20 Å, such as about 16 Å.

Applications

The present disclosure may be further understood by reference to thefollowing applications for high-quality silicon carbide films, whichapplications are intended to be purely illustrative. The presentdisclosure is not limited in scope by the specified applications, whichare simply illustrations of aspects of the present disclosure.

In some embodiments, a silicon carbide film may be deposited overexposed copper. In some embodiments in depositing the silicon carbidefilm, reaction conditions adjacent to the substrate can be free ofoxidants, such as O₂, O₃, and CO₂, including radicals thereof. Thus, thesilicon carbide film may be deposited directly over the exposed copperwithout oxidizing copper (e.g., creating cupric oxide). Such films canserve as etch stop layers, which can also serve as copper diffusionbarriers. The presence of the silicon carbide film can provide asufficiently low dielectric constant with excellent leakage propertiesto serve as a diffusion barrier. The silicon carbide film can be an etchstop and/or diffusion barrier either by itself or as a bilayer stack(e.g., SiCO/SiNC bilayer deposited over exposed copper). In someembodiments, the silicon carbide film can be placed in between adjacentmetallization layers that are typically produced by a damascene process.The silicon carbide film can resist etching and can be sufficientlydense to minimize the diffusion of copper ions into adjacent regions ofdielectric material. In some embodiments, nitrogen may be incorporatedinto the film by employing nitrogen-containing precursors or plasmaactivating nitrogen-containing radicals, such as elemental nitrogenradicals or amine radicals.

In some embodiments as shown in FIG. 1B, a silicon carbide film 111 canbe conformally deposited on features 112 of a substrate 110. Thefeatures 112 can be isolated or dense features, where the features 112can have relatively small critical dimensions (CD). In some embodiments,the features can have a CD that is equal to or less than about 20 nm,equal to or less than about 10 nm, or equal to or less than about 5 nm.The height to width aspect ratio of the features 112 can be greater than2:1, greater than 5:1, greater than 10:1, or greater than 20:1. The stepcoverage of the silicon carbide film 111 deposited on the features 112is at least 90%, at least 95%, or at least 99%.

In some embodiments, silicon carbide film may be deposited as verticalstructures adjacent to metal or semiconductor structures. Deposition ofsilicon carbide provides excellent step coverage along sidewalls ofmetal or semiconductor structures to create the vertical structures. Incertain embodiments, the vertical structures may be referred to asspacers or liners.

FIG. 1C illustrates a cross-section of silicon carbide liners depositedon the sidewalls of a gate electrode structure of a transistor. Asillustrated in FIG. 1C, the transistor can be a CMOS transistor with asilicon substrate 120 having a source 122 and a drain 123. A gatedielectric 124 can be deposited over the silicon substrate 120, and agate electrode 125 can be deposited over the gate dielectric 124 to formthe transistor. Silicon carbide spacers or liners 121 can be depositedon the sidewalls of the gate electrode 125 and gate dielectric 124.

In another example, FIG. 1D illustrates a cross-section of siliconcarbide deposited on sidewalls of exposed copper lines in an air gaptype metallization layer. Air gaps 130 can be introduced into anintegrated circuit layer between copper lines 132 that can reduce theeffective k-value of the layer. Silicon carbide liners 131 can bedeposited on the sidewalls of the copper lines 132, and a nonconformaldielectric layer 133 can be deposited on the air gaps 130, liners 131,and copper lines 132. Examples of such air gap type metallization layerscan be described in U.S. Patent Application Publication No. 2004/0232552to Fei Wang et al., which is herein incorporated by reference in itsentirety and for all purposes.

In some embodiments, a silicon carbide film may be deposited on thesidewalls of patterned porous dielectric materials. Ultra low-kdielectric materials can be made from a porous structure. The pores insuch materials can provide areas for ingress of metal during depositionof subsequent layers, including the deposition of diffusion barrierscontaining a metal such as tantalum (Ta). If too much metal migratesinto the dielectric material, the dielectric material may provide ashort circuit between adjacent copper metallization lines.

FIG. 1E illustrates a cross-section of silicon carbide film as a poresealant for porous dielectric materials. A porous dielectric layer 142can have a plurality of trenches or vias cut into the porous dielectriclayer 142 to form pores 140. Silicon carbide film 141 can be depositedalong the pores 140 to effectively seal the pores 140. Sealing the pores140 with the silicon carbide film 141 can avoid damaging the porousdielectric layer 142 that may otherwise be incurred by other sealingtechniques using a plasma. The silicon carbide film 141 can besufficiently dense as a pore sealant and may include non-cyclicsilicon-containing precursors, such as PMDSO and TMDSO. In someembodiments, an etched dielectric material such as the porous dielectriclayer 142 may first be treated by a “k-recovery” process, which exposesthe porous dielectric layer 142 to UV radiation and a reducing agent.This recovery process is further described in commonly owned U.S. PatentApplication Publication No. 2011/0111533 to Varadaraj an et al., whichis incorporated by reference herein in its entirety and for allpurposes. In another “k-recovery” process, the porous dielectric layer142 can be exposed to UV radiation and a chemical silylating agent. Thisrecovery process is further described in commonly owned U.S. PatentApplication Publication No. 2011/0117678 to Varadarajan et al., which isincorporated by reference herein in its entirety and for all purposes.After exposing the pores 140 to the recovery treatment, which makes thesurface more hydrophilic and provides a monolayer of material, a layerof conformally deposited silicon carbide film 141 can be deposited toeffectively seal the pores 140 of the porous dielectric layer 142.

In some embodiments, a silicon carbide film may be deposited as an ultralow-k dielectric material itself. Ultra low-k dielectrics areconventionally defined as those materials that have a dielectricconstant lower than that of 2.5. In such configurations, the ultra low-kdielectric material of silicon carbide can be a porous dielectric layer.The pores of the dielectric layer can be introduced by using cyclic orcaged precursor molecules, including the cyclic siloxanes andsilsesquioxanes. In one example, the porosity of the ultra low-kdielectric layer of silicon carbide can be between about 20% and 50%.Further, the ultra low-k dielectric layer can have an average pore sizeof less than about 100 Å, such as between about 5 Å and 20 Å. Forexample, a cyclosiloxane ring can have a radius of about 6.7 Å. Whileincreasing the number and size of the pores can lower the dielectricconstant, the mechanical integrity of the dielectric layer can becompromised if it is too porous.

CONCLUSION

In the foregoing description, numerous specific details are set forth toprovide a thorough understanding of the presented embodiments. Thedisclosed embodiments may be practiced without some or all of thesespecific details. In other instances, well-known process operations havenot been described in detail to not unnecessarily obscure the disclosedembodiments. While the disclosed embodiments are described inconjunction with the specific embodiments, it will be understood that itis not intended to limit the disclosed embodiments.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, it will be apparent thatcertain changes and modifications may be practiced within the scope ofthe appended claims. It should be noted that there are many alternativeways of implementing the processes, systems, and apparatus of thepresent embodiments. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the embodiments arenot to be limited to the details given herein.

What is claimed is:
 1. A method of depositing a silicon carbide film ona substrate, the method comprising: providing a substrate in a reactionchamber; flowing a silicon-containing precursor into the reactionchamber towards the substrate, wherein the silicon-containing precursorhas (i) one or more Si—H bonds and/or Si—Si bonds, (ii) one or more Si—Cbonds, Si—N, and/or Si—O bonds, (iii) no C—O bonds, and (iv) no C—Nbonds; flowing a co-reactant into the reaction chamber along with thesilicon-containing precursor, wherein the co-reactant is a hydrocarbonmolecule; generating, from a hydrogen source gas, radicals of hydrogenin a remote plasma source that are generated upstream of thesilicon-containing precursor and the co-reactant; and introducing theradicals of hydrogen into the reaction chamber and towards thesubstrate, wherein the radicals of hydrogen are in a ground state toreact with the silicon-containing precursor and the co-reactant to forma doped or undoped silicon carbide film on the substrate, wherein thedoped or undoped silicon carbide film has a conformality of at least90%.
 2. The method of claim 1, wherein all or substantially all of theradicals of hydrogen in an environment adjacent to the substrate areradicals of hydrogen in the ground state.
 3. The method of claim 1,wherein the doped or undoped silicon carbide film is a doped siliconcarbide film of silicon oxycarbide (SiCO), silicon carbonitride (SiCN),or silicon oxycarbonitride (SiOCN).
 4. The method of claim 1, whereinthe hydrocarbon molecule has one or more carbon-to-carbon double bondsor triple bonds.
 5. The method of claim 4, wherein the hydrocarbonmolecule includes propylene, ethylene, butene, pentene, butadiene,pentadiene, hexadiene, heptadiene, toluene, benzene, acetylene, propyne,butyne, pentyne, or hexyne.
 6. The method of claim 1, wherein theco-reactant interacts with the silicon-containing precursor as anon-depositing species in the doped or undoped silicon carbide film. 7.The method of claim 1, wherein the silicon-containing precursor and theco-reactant are simultaneously flowed along the same flow path into thereaction chamber.
 8. The method of claim 1, wherein the doped or undopedsilicon carbide film has a conformality of at least 95%.
 9. The methodof claim 1, wherein the silicon-containing precursor includes analkylcarbosilane, a siloxane, or a silazane.
 10. A method of depositinga silicon carbide film on a substrate, the method comprising: providinga substrate in a reaction chamber; flowing a first organosiliconprecursor into the reaction chamber, wherein the first organosiliconprecursor has (i) one or more Si—H bonds and/or Si—Si bonds, and (ii)one or more Si—C bonds, Si—N bonds, and/or Si—O bonds; flowing a secondorgano silicon precursor into the reaction chamber, wherein the secondorganosilicon precursor includes (i) no Si—H bonds and (ii) no Si—Sibonds; generating, from a hydrogen source gas, radicals of hydrogen in aremote plasma source that are generated upstream of the firstorganosilicon precursor and the second organosilicon precursor; andintroducing the radicals of hydrogen into the reaction chamber andtowards the substrate, wherein the radicals of hydrogen are in a groundstate to react with the first organosilicon precursor and the secondorganosilicon precursor to form a doped or undoped silicon carbide filmon the substrate.
 11. The method of claim 10, wherein all orsubstantially all of the radicals of hydrogen are radicals of hydrogenin the ground state.
 12. The method of claim 10, wherein the doped orundoped silicon carbide film is a doped silicon carbide film of siliconoxycarbide (SiCO), silicon carbonitride (SiCN), or siliconoxycarbonitride (SiOCN).
 13. The method of claim 10, wherein a flow rateof the second organosilicon precursor is at least two times greater thana flow rate of the first organosilicon precursor.
 14. The method ofclaim 10, wherein a flow rate of the second organosilicon precursor isbetween about 25 sccm and about 200 sccm.
 15. The method of claim 10,wherein the doped or undoped silicon carbide film has a conformality ofat least 95%.
 16. The method of claim 10, wherein the secondorganosilicon precursor includes tetramethylsilane (4MS).
 17. The methodof claim 10, wherein the second organosilicon precursor interacts withthe first organosilicon precursor as a depositing species in the dopedor undoped silicon carbide film.
 18. The method of claim 10, wherein thefirst organosilicon precursor and the second organosilicon precursor aresimultaneously flowed along the same flow path into the reactionchamber.
 19. The method of claim 10, wherein each of the firstorganosilicon precursor and the second organosilicon precursor is floweddownstream from the remote plasma source.
 20. The method of claim 10,further comprising: flowing a co-reactant from the remote plasma sourceand upstream of the first organosilicon precursor and the secondorganosilicon precursor to provide radicals and/or ions of theco-reactant, wherein the co-reactant includes carbon dioxide (CO₂),carbon monoxide (CO), water (H₂O), methanol (CH₃OH), oxygen (O₂), ozone(O₃), nitrogen (N₂), nitrous oxide (N₂O), ammonia (NH₃), or mixturesthereof.